Prestressed tank and method of producing same

ABSTRACT

A prestressed tank including a substantially vertical shell with a layer of cementitious material on each side thereof. The shell comprises a plurality of panels having edges cooperating to form joints. A sealant may be pumped into channels within the joints after application of said layers to the shell to fill voids and veins within the layers. Sealant is also disposed adjacent to and/or around reinforcing rods and wires disposed in the cementitious material.

United States Patent [191 Crom, Jr.

[111 3,822,520 [451 July 9,1974

[ PRESTRESSED TANK AND METHOD OF PRODUCING SAME [76] Inventor: John M. Crom, Jr., 720 Champagne Dr., Incline Village, Nev. 89450 [22] Filed: Jan. 20,1970 [21] Appl. No.: 4,389

Related US. Application Data [63] Continuation of Ser. No. 586,277, Oct. 12, 1966,

abandoned.

[52 U.S.Cl. .Q 52/224, 52/744 51 Int. Cl E04h 12/16 58 Field of Search 52/223-230,

[,56] References Cited UNITED STATES PATENTS 1,683,025 9/1928 Dallam 52/249 2,370,780 3/1945 Crom 52/224 X Primary Examiner-Frank L. Abbott Assistant Examiner-Henry L. Raduazo Attorney, Agent, or Firm-Stevens, Davis, Miller and Mosher [5 7] ABSTRACT A prestressed tank including a substantially vertical shell with a layer of cementitious material on each side thereof. The shell comprises a plurality of panels having edges cooperating to form joints. A sealant may be pumped into channels within the joints after application of said layers to the shell to fill voids and veins within the layers. Sealant is also disposed adjacent to and/or around reinforcing rods and wires disposed in the cementitious material.

13 Claims, 10 Drawing Figures PATENTEB L 91974 3,822,520

SHEET 1 or 5 w WNW AWMAVWWWAWW m m A A'Q A PATENTEDJUL 9 I974 SHEET 2 (IF 5 www.

PATENTEDJUL 9:914

SHEET 3 BF 5 PATENTEUJUL 3.822520 sum 5 BF 5 FIG. 8.

SYNTHETIC RES/N IN PRESTRESSED TANK AND METHOD OF PRODUCING SAME Prestressed composite tanks are widely used for storage of liquids and other purposes. Such tanks normally' include a light gage steel shell which is incased in layers of cementitious material such as gunite. The outer wall is usually wrapped with prestressed wire which is enclosed by a cover coating of gunite or the like. These tanks have become accepted in the industry and have been recognized as relatively trouble free.

" Generally. speaking, the shell is constructed of a plurality' of interlocking panels which are united by some type of book joint. Heretofore, these joints have been sealed with a mastic orcaulking compound. Sometimes, the mastic has been partially applied in the joint at the time that the panels are erected and additional mastic is applied to-either one or both sides of the erected shell. Such sealingoperations have not been entirely successful. In cases where a liquid gets into one of these joints, there is then a path the height of the shell which the liquid may follow within the joint. Water or other liquid in the joints may then leak out through any cracks which intercept the vertical joint. A leak under such circumstances is likely to be worse than if no shell had been employed.

In the present invention, it is proposed to alleviate this problem by providing channels in the joints extending the length of the panel-s, which channels may be filled with a sealant. For example, after gunite or the like has been applied against one face of the shell; the channels are cleared of any gunite which may have formed an obstruction. Means are then provided to prevent entrance of gunite into the channels when the gunite layer. is applied to the other face of the shell. Subsequently, sealant is pumped into the channels to entirely fill the channels.

It has also been a problem in the industry to avoid the creation of voids at numerous places in the gunite walls. Frequently, the voids are interconnected thus presenting a network of veins or fissures in whichliquid can travel for considerable distance when under pressure. Thus, the leakage may first appear at a point some distancefrom the point of entry of the liquid into the wall. The voids are likely to occur as sand pockets behind reinforcing rods which are conventionally employed in such tanks, and also behind the annular wraps of prestressed wire when a finish coating is applied to cover the prestressed wire. If a fluid can find its way from within the tank to a void along a reinforcing rod in the wall, it can burst out at weak spots to veins adjacent the wire. From there it can be distributed over wide areas causing many fine leaks.

In accordance with the present invention, it is proposed to inject a sealant of the type used in the channels of the shell joints into selected regions behind the reinforcing rods. Since the sealant is under pressure,

continued pumping will force sealant into any vein network that might exist inthese areas.

ite covering.

With regard to veins formed behind the annular prestressing wire, there havebeen a number of remedies proposed including the use of fine masonry sand in the gunite in the expectationthat the voiding behind the wire can be minimized. Other proposed alternatives include incasing the wire in a substantially uniform plastic sheathing or spraying a slurry coating over the wires before applying the gunite cover coating. Although these proposals have met with some degree of success, each of these methods has disadvantages. For example, it is thought that using a slurry leads to excessive shrinkage, low strength and high void content in the coating, and that there may be a poor bond between the cover coating and the layer formed from the slurry. Incasing the wire in a substantially uniform plastic sheathing does not eliminate the voids in the gunite beneath the wire. Furthermore, assuming that a layer of gunite is to be applied over the wire, there may be a poor bond to the plastic sheathing.

In accordance with the present invention, a controlled amount of flowable resinous'material is applied to the wire as it is wrapped around the wall or, preferably, just after it is put in place on the wall. In the latter case, the resinous material coats the wire only where it does not touch the wall, however, it may flow by capillaryaction into the small spaces underneath the wire to eliminate such voids and leakage: paths. Sand grits or the like may be partially embedded in the resinous material while it is still tacky to improve the bond between the resinous material and the subsequently applied gun- It is a primary object of this invention to provide an improved prestressed composite tank having superior leak-proof characteristics.

Another object of this invention is to provide a'prestressed composite tank having improved means for sealing joints in the shell.

Still another object of the invention is to provide sealant in voids in the wall of the tank behind reinforcing bars.

A further object of the invention is to provide a tank structure in which a resinous material has been applied to the prestressing wire.

Another principal object of the invention is to provide an improved method for constructing prestressed composite tanks.

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed. description taken in conjunction with the drawings in which:

FIG. 1 is a vertical cross-sectional view illustrating one embodiment of a prestressed composite tank constructed in accordance with the present invention;

FIG. 2 is a horizontal cross-sectional view through the wall of the tank taken on the line 22 of FIG. 1;

FIG. 3 is a horizontal cross-sectional view taken on the line 3-3 of FIG. 1 and illustrates a tube for pumpthe means for pumping sealant behind the vertical reinforcing bars;

FIG. 6 is an elevational view of a modified shell having horizontal joints between overlapping vertical panline 7-7 of FIG. 6 showing the details of one of the horizontal joints;

FIG. 8 is a horizontal cross-sectional view illustrating I the positioning of the prestressed wire;

FIG. 9 is a partial plan view of the arrangement shown in FIG. 8; and

FIG. 10 is a detail view on an enlarged scale illustrating the coating applied around the prestressed wire after the surface of the coating has been roughened by partially embedding coarse particles therein.

The principal components of a conventional prestressed composite tank will be described before proceeding to a discussion of applicants improvements. The tank is a substantially integral structure comprising a cylindrical wall generally designated by reference numeral 20, a floor 22, and a roof or dome 24. The lower end of the wall is rounded into a fillet section 26 at the juncture with the floor 22. The upper end 28 of the wall is of enlarged diameter to provide additional support for the dome 24.

Proceeding from the interior of the tank outwardly, the wall comprises an inner layer 30 of a cementitious material such as gunite, a metal shell or diaphragm generally designated by reference numeral 32, an intermediate layer 34 of gunite or similar material, a plurality of passes of prestressed wire 36 wrapped around the intermediate layer 34, and a cover layer 38 of gunite or similar material.

Reinforcing rods 40 and 42 are embedded in the intermediate layer 34. The rods 40 have integral upper extensions 44 projecting into the dome 24 and lower extensions 46 projecting into the floor 22. Similarly, the shorter rods 42 have upper extensions 48 within the dome and lower extensions 50 within the floor. As shown in FIG. 5, there are three short rods 42 between each pair of reinforcing rods 40. It will be understood that this arrangement is merely for purposes of illustration. If desired, the floor 22 may be further reinforced by horizontal reinforcing rods 52.

Referring now to FIG. 2, the shell 32 is formed of a plurality of interlocking corrugated panels. Substantially planar panel sections 54, 56, 58 and 60 form the bottoms of alternately oppositely opening corrugations with the flaring sides of the corrugations formed by reverse bent connecting portions 62, 64 and 66. Hooks 68, 70 are provided at opposite ends of each panels with the-hook 68 of one panel cooperating with the complementarily shaped hook 70 of an adjacent panel. A compressible cord 72 is squeezed into the opening between hook 70 and the adjacent panel section 60 to form an elongated substantially triangular channel which is filled with a sealant 74. The compressible cord 72 functions as a gasket and is made of sponge rubber or a synthetic plastic foam. Plastic foams of suitable characteristics and the procedures for making same are well known. The cord can be not only circular in cross section, but oval or other geometric shapes, and can also be in the form of a hollow tube.

The function of cord 72 and the positioning of sealam 74 will now be described. In constructing the tank, the shell 32 may be erected without putting any caulking or sealant on either the interior or exterior surfaces of the shell. The shell is supported by a suitable falsework. Cementitious material such as gunite is shot against the exterior face of the shell to form the intermediate layer 34. After removing the falsework from the inside of shell 32, the openings between hooks and panel sections 60 are cleared of any obstructions such as Cementitious material which might have washed into the joint from the exterior face. The joint openings may be sand blasted and/or primed to inhibit rusting and to give a good surface for promoting adhesion of the sealant. At this point the compressible cords 72 are inserted into the joint openings to prevent the entrance of Cementitious material during the formation of the inner layer 30. One end of a tubing 76 is inserted into the bottom of each joint and extends upwardly behind the cord 72. At the upper end of each joint, an end of a tubing 78 is similarly inserted into the joint. Tubings 76 and 78 which may be made, for example, of copper are of sufficient length to extend through the wall section 26 and the inner face of dome 24 of the finished tank. It is presently preferred to complete the interior wall of the tank, to wait several weeks permitting the gunite to obtain its maximum strength, and to thereafter circumferentially prestress the tank before applying the sealant 74. The sealant is applied by pumping under pressures in the order of 50 psia. through input tubing 76. The pumping is continued until sealant appears at the outlet of tubing 78. Delaying the pumping of the sealant until this stage in the construction is considered advantageous since the circumferential compression caused by the wound pre stressed wire gives-additional arch strength to the gunite and reduces the possibility of separation of the gunite from the shell during the sealant pumping operation. Also, the sealant may be effective to fill any cracks which might appear during the wire winding operation as well as possible shrinkage cracks and the like. The use of a compressible material for the cord 72 is advantageous since, in the event of blockage of the channel for the sealant, the pressurized sealant may compress the cord material to establish a flow path past the blocked point. It is also theorized that the cord material, after compression by the pressure of the sealant, acts in the nature of an accumulator and continues to keep the sealant under pressure after termination of the pumping and after the top and bottom tubes are sealed to minimize the presence of voids if some of the sealant should seep away from the joints. The above is offered by way of explanation only and it is not applicants intention to be in any way limited by the veracity of the theory.

The sealant 74 may be grout or synthetic resin. Preferably, the sealant is a relatively low viscosity two component epoxy resin forming material containing no solvent with no shrinkage upon setting.

A portion of the same material used as a sealantin the shell joints may also be utilized to seal voids behind the reinforcing rods 40 and 42. These voids are often produced because the gunite stream does not get fully around the back of the rods and large voids may be formed in the shadow of the gunite stream. For sealing such voids, one end of a rubber tubing 80 is inserted into the bottom of each shell joint adjacent to the end of the sealant input tubing 76. A portion of each tubing 80 is secured to the rear of an adjacent reinforcing bar 40 by wiring 82 or other suitable securing means such as tape, clamps, etc. As shown in FIG. 5, the tube is of looped configuration with upright portions 84 secured to the rear of the shorter reinforcing rods 42 by wiring 86 or other suitable securing means. The tubing 80 terminates in an end section 88 which is secured by wiring 90 to a section of the reinforcing rod 40 adjacent the next shell joint. Each section of the tubing which is secured to a reinforcing rod 40 or 42 has a pair of slits 92 as is best seen in FIG. 3. Of course, only one slit or other aperture per-section is really necessary. When sealant is pumped into the shell joints via tubings 76, a portion of the sealant will pass through tubings 80 and out through the slits 92 to form a sealant mass 94 behind each reinforcing rod 40 and a sealant mass 96 behind each reinforcing rod 42. These sealant masses function to prevent fluid from finding a crack or network of cracks which may extend uninterruptedly essentially the height of the tank.

- As isevident in FIG. 1, similar means are providedto place sealant masses 94 and 96' behind the upper ends of reinforcing rods 40 and 42 respectively. Accordingly, primed reference numerals are employed to des-.

ignate parts corresponding to those described previously in connection with placing sealant behind the lower ends of the reinforcing rods. In this case, it is evident that the sealant from the upper end of the shell joints passes into tubings 80' and out through slits 92'.

Tubings 80 and 80' may also be of sufficient length to extend through the tank wall rather than terminate at the shell joints. In this case, sealant may be pumped into tubings 80 and 80' independently of the sealant supplied to the shell joints.

FIGS. 4(a) through (f) illustrate various modified shell joint constructions in accordance with the present invention. In FIG. 4(a), the sides of the panels forming the shell 32(a) have oppositely flaring lips which cooperate to form a triangular channel 102 which is adapted to be filled with sealant. The mouth of the channel 102 is closed by a compressible cord 72 as described in connection with the FIG. 2 embodiment. A tape 104 may be applied to the exterior face of the shell to prevent gunite from the layer34 flowing into the channel 102. The tape 104 is optional since the channel may be cleaned after the layer 34 has set.

The structure shown in FIG. 4( b) is similar to that of FIG; 4(a) with the exception that the shell 32(b) is formed of panels having abuttingbeads 106, 108 and flaring lips 110, 112 which form a channel for the reception of the cord 72. A tape 114 which covers the beads 106, 108 is optional.

In FIG. 4(c), the shell 32(c) has the abutting panel edges bent to form openings 116, I18 and cooperating lips 120, 122 into which the cord 72 is inserted. The openings 116, 118 enable additional keying of the inner layer 30 of the wall to the shell.

' In FIG. 4(d), interlocking sections 124, 126 of adjacent panels form a substantially rectangular channel for the reception of the expansible cord 72. In this embodiment, care must be taken that the cord 72 is not pushed to the bottom of the channel either during insertion or during the formation of the inner layer 300i" the wall.

In FIG. 4(e), the shell 32(e) consists of interlocked panels each having at one end an outwardly projecting lip 128 which is receiving within a hook 130 of the adjacent panel. The cord 72 is inserted into the channel between lip 128 and hook 130.

FIG. 4(f) illustrates an embodiment in which the shell 32(f) consists of panels having cooperating bent portions 132, 134 which form a substantially enclosed triangular channel 136 for the reception of sealant. Tapes 138, 140 prevent entry of gunite into channels 136 during the formation of the layers 34, 32, respectively. In this embodiment there is no opening in the joint that would permit the use of a cord gasket.

FIGS. 6 and 7 illustrate anotherembodiment of the present invention which is useful on high tanks where one shell panel cannot extend the entire height of the tank. In this embodiment, alternate bottom shell panels 140, 142 are of different heights and are overlapped by upper shell panels 144 and 146, respectively. A pair of spaced parallel expansible cords 148, are positioned within the overlap of the shell panels to form channels for the subsequent reception of a sealant 152 as shown in FIG. 7. Sheet metal screws 154 extend through the overlapped panel edges and compress the cords in the process of uniting the panels. The vertical joints between the panels generally designated by reference numeral 156 may be substantially identical in construction to the joints illustrated in FIGS. 2 or 4 and described above. A flow path for sealant between the vertical joints and the horizontal joints may be established by providing a small aperture in the upper left hand corners of panels 140, 142 where they are overlapped by the upper panels 144, 146.

In this embodiment, sealant input and outlet lines are inserted into the lower and upper ends of the vertical joints 156 substantially as described in connection with the FIG. 1 embodiment. To seal the horizontal and vertical joints, after the gunite layers are applied, the sealant is initially pumped upwardly in the lower section of a vertical joint 156 as shown by the arrows in FIG. 6. When the sealant reaches the level of a horizontal joint, a portion of the sealant flows horizontally within the channel between cords 148, 150. To avoid air pockets, the cord 150 may terminate and a block 158 provided just before the next vertical joint 156. When the hori zontal joint has been filled with sealant, some sealant may flow out a tube 159 at the end of the cord 150. At this time the tube may be pinched off or pumping resumed into tube 159 at this intermediate level. The pumping may now be continued until the upper half of the vertical joint is filled and sealant flows out of the top of the joint. The above described pumping sequence is repeated until all of the joints have been sealed.

In a presently less preferred embodiment, the horizontal joint could be a loose overlap with compressible cords or tape across the openings to the channel to prevent gunite blocking the channel.

FIGS. 8 and 9 illustrate the wrapping of the prestressed wire 36 around the intermediate layer 34. Reference numeral 160 designates a wire spacing device of known construction, and hence will not be described in detail in this specification. A suitable wire spacing device is disclosed in US. Pat. No. 2,370,780 to J. M. Crom. The wire 36 is supplied to the spacing device 160 from a suitable supply spool as indicated in FIG. 8 and is prestressed in the known way. In this regard, an end of the wire 36 is mechanically anchored by known means such as shown at 151 in FIG. 14 US. Pat. No. 2,370,780 to the layer 34 at a starting point thereon adjacent to the base or top of the tank and the device 160 then carries the free portion of the wire and winds it 7 tautly around the layer 34 up to an end point of the desired winding, at which end point the wire 36 is again mechanically anchored to the layer 34 so as to permanently maintain the prestress tension in the length of wire between said starting and end points of the winding. A synthetic resin applicator 162 is suitably secured to the wire spacing device 160. A conduit 164 supplies the applicator with synthetic resin from a source such as a pump (not shown) geared to the forward motion of the device 160. The resin is discharged through a nozzel 166 onto the preceding wrap of wire 36. Although the resin could be applied to the wire as the wire is being-wrapped upon layer 34, there is usually some wiping action of the wire against the wall after its initial contact due to sway of the machine and to irregularities in the motion of the wire itself, which variations are avoided in applying the resin to the preceding wrap of wire. As isevident from FIG. 10, the resin forms a coating 168 about the wire 36 except where it is in contact with layer 34. Since the resin is flowable at the time of application, the coating 168 may flow into small spaces underneath or adjacent to the wires 36 .to minimize voids and leakage paths. The resinous material employed to form coating 168 may be an epoxy resin, a varnish or paint or similar material. In order to improve the adherence of gunite to epoxy resins or other resinous material used to form coating 168,

' the surface of coating 168 is preferably roughened by partially embedding particles 170 such as sand grits in the coating while it is still tacky. The particles may be applied to the coated wires using a hawk which .is well known in the trades to project the sand in a low velocity air current against the coating. The roughened surface of the coating improves the adherence of the outer layer 38 to the coated wire.

The function of the resin coating is strictly protective since the prestress tension in the wire 36 is permanently maintained by the fact that the wire is mechanically anchored at its opposite ends to the layer 34. Corrosion of prestressed wire has been a serious problem in certain areas of the country and the gunite overcoat 38 has been insufficient to adequately protect the wire against such corrosion.

The wire 36 is not placed in a groove in layer 34 nor is there any deliberate attempt made to effect a bonding of the wire 36 to the surface of layer 34 with the resin acting as an adhesive. As a matter of fact, the surface of layer 34 is usually so rough and irregular that the prestressing wire only contacts the high spots along the surface of layer 34. The wire may be free-spanning between the high spots so that the resin does not even necessarily contact the surface of layer 34.

While preferred embodiments of the present invention have been shown and described, it will be appreciated that many changes and modifications may be made therein without departing from the scope and spirit of the invention. For example, principles of the invention may be utilized in other structures such as poured concrete tanks, tanks without roofs such as sewage digesters, water clarifiers and the like, and designs in which the wall is not internally connected with the roof and floor. It is intended to encompass all such changes and modifications as fall within the scope of the appended claims.

. What is claimed is:

l. A prestressed tankcomprising a wall and means cooperating with said wall to define a storage area, said wall comprising a substantially vertical shell and a layer of cementitious material on each side of said shell, said shell being formed of a plurality of panels arranged successively adjacent to each other with each pair of adjacent edge portions thereof interengaging each other to form a respective joint including a hollow channel extending along substantially the full length of said edge portions, said channel being closed along its length relative to said cementitious material, respective conduit means leading from the opposite ends of said channel to outwardly of said cementitious material, a sealant substantially completely filling said channel.

2. A tank according to claim 1, further comprising a plurality of reinforcing rods positioned in one of the layers of cementitious material, at least some of said joints and channels being vertical, a plurality of tubes each having one end disposed in the lower end of a vertical channel and adapted to provide a flow path for sealant, each tube having portions thereof embedded in said one layer adjacent at least one of said reinforcing rods, and each of said portions of said tubes being provided with aperture means for the discharge of sealant in the vicinity of said reinforcing rods.

3. A tank according to claim 1, including a compressible cord between a said pair of edge portions and together therewith closing said channel relative to said cementitious material.

4. A tank according to claim 1, wherein certain of said joints are vertical joints, and tape means extending the length of said joints to prevent the entry of cementitious material into said channels during the application of said layers of cementitious material to said shell.

5. The tank of claim 1, wherein certain of said joints are horizontal and each includes a said channel defined by vertically overlapping edge portions of vertically succeeding panels and by a closure means extending along the horizontal extent of said overlapping edge portions to close the upper and lower sides of said channel relative to said cementitious material.

6. A tank according to claim 1, wherein said joints include horizontal joints each having a horizontal channel, said horizontal joints comprising overlapped edge portions of adjacent panels, a pair of spaced substantially parallel compressible members disposed within the overlap of the edge portions of said panels, means extending through the overlapped edge portions of said panels and compressing said members, said horizontal channels being defined by the overlapped edge portions and said compressible members.

7. A tank accordingto claim I, further comprising a plurality of wraps of prestressed wire encircling the outer layer of said layers of cementitious material, a resinous covering around each of said wraps of prestressed wire, and a layer of cementitious material disposed over said resinous covering.

8. A prestressed tank comprising a wall and means cooperating with said wall to define a storage area, said wall comprising a substantially vertical shell and a layer of cementitious material on each side of said shell, said shell being formed of a plurality of panels, the edges of adjacent panels cooperating to form joints, said joints comprising means forming channels extending substantially the length of the respective joint, means to enable sealant to be pumped into said channels after at least one of said layers has been applied to said shell, 21 sealant substantially completely filling said channels, a plurality of reinforcing rods positioned in one of the layers of cementitious material, a plurality of tubes each having portions thereof embedded in said one layer adjacent at least one of said reinforcing rods, means to supply sealant into one end of each of said tubes, and each of said portions of said tubes being provided with aperture means for the discharge of sealant in the vicinity of said reinforcing rods.

9. in a method of constructing a prestressed tank, the improvement which comprises erecting an annular shell of a plurality of panels having edges cooperating to form joints enclosing vertical channels extending substantially the length of the joints, placing tubular means into communication with said channels, applying a layer of cementitious material to each side of said shell, and thereafter pumping a sealant through said tubular means into said channels to seal same.

10. A method according to claim 9, further comprising placing at least one compressible member into each joint during its formation to define at least one surface of a respective channel.

11. In a method of constructing a prestressed tank, the improvement which comprises erecting an annular shell of a plurality of panels having edges cooperating to form joints enclosing vertical channels extending substantially the length of the joints, placing tubular means into communication with said channels, applying a layer of cementitious material to each side of said shell, thereafter pumping a sealant through said tubular means into said channels to seal same, positioning reinforcing rods in one of the two layers of cementitious material, embedding a plurality of tubular members in said one layer with apertured portions thereof adjacent sections of said reinforcing rods, and pumping sealant through said tubular members into regions adjacent said reinforcing rods.

12. A method according to claim 9, further comprising wrapping a prestressed wire around one of the two layers of cementitious material, coating the wrapped prestressed wire with a resinous coating, and applying a layer of cementitious material over said resinous coating.

13. A method for constructing a reinforced structure comprising positioning a plurality of reinforcing rods in cementitious material, embedding a plurality of tubes in'said cementitious material with apertured portions of each of said tubes adjacent at least one of said reinforcing rods, setting said cementitious material, and pumping a sealant through said tubes and out said apertured portions into regions adjacent said reinforcing rods. 

1. A prestressed tank comprising a wall and means cooperating with said wall to define a storage area, said wall comprising a substantially vertical shell and a layer of cementitious material on each side of said shell, said shell being formed of a plurality of panels arranged successively adjacent to each other with each pair of adjacent edge portions thereof interengaging each other to form a respective joint including a hollow channel extending along substantially the full length of said edge portions, said channel being closed along its length relative to said cementitious material, respective conduit means leading from the opposite ends of said channel to outwardly of said cementitious material, a sealant substantially completely filling said channel.
 2. A tank according to claim 1, further comprising a plurality of reinforcing rods positioned in one of the layers of cementitious material, at least some of said joints and channels being vertical, a plurality of tubes each having one end disposed in the lower end of a vertical channel and adapted to provide a flow path for sealant, each tube having portions thereof embedded in said one layer adjacent at least one of said reinforcing rods, and each of said portions of said tubes being provided with aperture means for the discharge of sealant in the vicinity of said reinforcing rods.
 3. A tank according to claim 1, including a compressible cord between a said pair of edge portions and together therewith closing said channel relative to said cementitious material.
 4. A tank according to claim 1, wherein certain of said joints are vertical joints, and tape means extending the length of said joints to prevent the entry of cementitious material into said channels during the application of said layers of cementitious material to said shell.
 5. The tank of claim 1, wherein certain of said joints are horizontal and each includes a said channel defined by vertically overlapping edge portions of vertically succeeding panels and by a closure means extending along the horizontal extent of said overlapping edge portions to close the upper and lower sides of said channel relative to said cementitious material.
 6. A tank according to claim 1, wherein said joints include horizontal joints each having a horizontal channel, said horizontal joints comprising overlapped edge portions of adjacent panels, a pair of spaced substantially parallel compressible members disposed within the overlap of the edge portions of said panels, means extending through the overlapped edge portions of said panels and compressing said members, said horizontal channels being defined by the overlapped edge portions and said compressible members.
 7. A tank according to claim 1, further comprising a plurality of wraps of prestressed wire encircling the outer layer of said layers of cementitious material, a resinous covering around each of said wraps of prestressed wire, and a layer of cementitious material disposed over said resinous covering.
 8. A prestressed tank comprising a wall and means cooperating with said wall to define a storage area, said wall comprising a substantially vertical shell and a layer of cementitious material on each side of said shell, said shell being formed of a plurality of panels, the edges of adjacent panels cooperating to form joints, said joints comprising means forming channels extending substantially the length of the respective joint, means to enable sealant to be pumped into said channels after at least one of said layers has been applied to said shell, a sealant substantially completely filling said channels, a plurality of reinforcing rods positioned in one of the layers of cementitious material, a plurality of tubes each having portions thereof embedded in said one layer adjacent at least one of said reinforcing rods, means to supply sealant into one end of each of said tubes, and each of said portions of said tubes being provided with aperture means for the discharge of sealant in the vicinity of said reinforcing rods.
 9. In a method of constructing a prestressed tank, the improvement which comprises erecting an annular shell of a plurality of panels having edges cooperating to form joints enclosing vertical channels extending substantially the length of the joints, placing tubular means into communication with said channels, applying a layer of cementitious material to each side of said shell, and thereafter pumping a sealant through said tubular means into said channels to seal same.
 10. A method according to claim 9, further comprising placing at least one compressible member into each joint during its formation to define at least one surface of a respective channel.
 11. In a method of constructing a prestressed tank, the improvement which comprises erecting an annular shell of a plurality of panels having edges cooperating to form joints enclosing vertical channels extending substantially the length of the joints, placing tubular means into communication with said channels, applying a layer of cementitious material to each side of said shell, thereafter pumping a sealant through said tubular means into said channels to seal same, positioning reinforcing rods in one of the two layers of cementitious material, embedding a plurality of tubular members in said one layer with apertured portions thereof adjacent sections of said reinforcing rods, and pumping sealant through said tubular members into regions adjacent said reinforcing rods.
 12. A method according to claim 9, further comprising wrapping a prestressed wire around one of the two layers of cementitious material, coating the wrapped prestressed wire with a resinous coating, and applying a layer of cementitious material over said resinous coating.
 13. A method for constructing a reinforced structure comprising positioning a plurality of reinforcing rods in cementitious material, embedding a plurality of tubes in said cementitious material with apertured portions of each of said tubes adjacent at least one of said reinforcing rods, setting said cementitious material, and pumping a sealant through said tubes and out said apertured portions into regions adjacent said reinforcing rods. 